#include <stdio.h>

int main() {
  int number;
  printf("Please Enter the Value of 'n' : \n");
  scanf("%d",&number);

  printf("\nThe sum is: %d\n", getSum(number) );
  return 0;
}

int getSum(int n) {
    int sum;

    sum = (n % 2 == 0) ? -(n / 2) : (n + 1) / 2;

    /* if (n%2 == 0)
    then, -(n / 2)
    else, (n+1) / 2
    */

    return sum;
}